I'm by no means an expert but my specialist (very knowledgeable, reputable and conservative when it comes to treatment recommendations) said there is no identifiable evidence that MRIs are harmful.

I'm almost at the 6-month mark post-injury and struggle with exertion as well. My symptoms are mostly pretty low-level at rest, sometimes almost negligible, but I still have issues with physical and sometimes mental exertion. My doc recommends rest and only very gradually increasing exertion, and backing off if symptoms are triggered.

He's curious about the U Buffalo exercise program, but is skeptical and thinks there isn't enough evidence yet to support it. At present, he says, all we know is that a patient's ability to exert himself or herself is an index of recovery; there isn't enough evidence to conclude that exertion is a means of facilitating recovery. Light activity or exercise is good, he says, so long as it doesn't cause symptoms to flare up. The goal should be to remain sub-threshold of symptoms.